In a conventional selective call communication system, selective call signals are received at a predetermined baud rate by at least one selective call receiver. Upon receiving a selective call signal, a selective call receiver typically performs a baud rate detection. Performing the baud rate detection allows verification of a selective call signal before the selective call receiver decodes a selective call message encoded within the selective call signal.
Under normal operating conditions, selective call signals are subjected to noise interferences and have duty cycle offsets. A typical baud rate detection ensures that a selective call signal meets certain signal quality criteria before it is processed. Otherwise, a selective call signal that is noisy or with bad duty cycle offsets can be processed incorrectly.
One typical criterion of a baud rate detection is a pass and fail grading of a selective call signal in terms of duty cycle offsets. However, a pass or fail criterion does not reliably grade a selective call signal that is at a signal threshold level with varying levels of duty cycle offsets. Depending on the operating conditions of a selective call receiver, varying levels of duty cycle offsets can be acceptable.
Baud rate detections also allow a selective call receiver to conserve current. For example, when a baud rate detection fails, the selective call receiver can inactivate its receiver circuit so as not to continue receiving a selective call signal. As the receiver circuit of a selective call receiver consumes a large portion of available current, inactivating the receiver circuit therefore saves current.
Thus, what is needed is a method to reliably grade a selective call signal in a selective call receiver, and thereby reduce its current consumption by adopting optimum operating conditions.